The N6-methyladenosine (m6A) modification is crucial for plant development and stress responses. In rice, the male sterility caused by the deficiency of OsFIP37, a core component of the m6A methyltransferase complex, highlights the importance of m6A in male fertility. m6A is a reversible modification that can be removed by m6A demethylases. However, the role of mRNA m6A demethylase in rice male fertility remains unclear. This study identifies OsALKBH9 as an mRNA m6A demethylase and demonstrates its involvement in male fertility regulation. Knockout of OsALKBH9 causes male sterility, dependent on its m6A demethylation activity. Cytological analysis reveals defective tapetal programmed cell death (PCD) and excessive accumulation of microspore exine in Osalkbh9-1. Transcriptome analysis shows up-regulation of genes involved in tapetum development, sporopollenin synthesis, and transport pathways in Osalkbh9-1. Additionally, OsALKBH9 demethylates the m6A modification in TDR and GAMYB transcripts, affecting their stability and leading to excessive accumulation of pollen exine. These findings highlight the precise control of mRNA m6A modification and reveal the pivotal roles of OsALKBH9-mediated m6A demethylation in tapetal PCD and pollen exine accumulation in rice.The N6-methyladenosine (m6A) modification is crucial for plant development and stress responses. In rice, the male sterility caused by the deficiency of OsFIP37, a core component of the m6A methyltransferase complex, highlights the importance of m6A in male fertility. m6A is a reversible modification that can be removed by m6A demethylases. However, the role of mRNA m6A demethylase in rice male fertility remains unclear. This study identifies OsALKBH9 as an mRNA m6A demethylase and demonstrates its involvement in male fertility regulation. Knockout of OsALKBH9 causes male sterility, dependent on its m6A demethylation activity. Cytological analysis reveals defective tapetal programmed cell death (PCD) and excessive accumulation of microspore exine in Osalkbh9-1. Transcriptome analysis shows up-regulation of genes involved in tapetum development, sporopollenin synthesis, and transport pathways in Osalkbh9-1. Additionally, OsALKBH9 demethylates the m6A modification in TDR and GAMYB transcripts, affecting their stability and leading to excessive accumulation of pollen exine. These findings highlight the precise control of mRNA m6A modification and reveal the pivotal roles of OsALKBH9-mediated m6A demethylation in tapetal PCD and pollen exine accumulation in rice.